Electroplating barrel



Oct. 20, 1964 w. H. JACKSON ELECTROPLATINGBARREL 2 Sheets-Sheet 1 Filed Dec. 12, 1962 INVENTOR. M77147?! H J'Zciis'ofi Oct. 20, 1964 w. H. JACKSON 3,153,624

ELECTROPLATING BARREL Filed Dec. 12, 1962 2 Sheets-Sheet 2 I J3 4d INVENTOR. r 1447/ 7 7! S, fic/isow 13W a "14: firm/2V:

United States Patent 3,153,624 ELECTRGPLATENG BARREL William H. Jackson, Birmingham, Mich, assignor to The Udylite Corporation, Detroit, Mich, a corporation of Delaware Filed Dec. 12, 962, Ser. No. 244,04h 12 Claims. (Cl. 204-213) The present invention broadly relates to liquid treating apparatus and more particularly to an improved barrel construction suitable for transporting bulk quantities of small workpieces through a liquid treating operation such as an electroplating operation.

Treating barrels and more specifically electroplating barrels of the general type comprising the present invention are in widespread use in industry for treating bulk quantities of small workpieces which, because of their small size, cannot be efficiently and economically handled individually. Treating barrels of this type conventionally comprise a plurality of side panels and end walls which define a chamber of polygonal cross-sectional shape including a plurality of longitudinally extending corners as defined by supporting rails to which the side edges of the individual panels are secured. The barrels are supported on a suitable framework and are rotatably driven while immersed in a suitable treating solution whereby a tumbling action is imparted to the bulk quantity of small workpieces therein.

In order to facilitate contact of the surfaces of the workpieces being treated with the liquid treating solution in which the treating barrel is immersed, the panels comprising the wall portions of the treating barrel are conventionally provided with a plurality of perforations therethrough through which the treating solution enters and drains from the interior of the treating barrel. The efficiency and uniformity of the surface treatment of workpieces in treating barrels heretofore known have in many instances been less than desirable because of poor solution circulation into and out of the interior of the treating barrel and around and between the workpieces contained therein.

This problem is particularly pronounced when relatively small workpieces are being treated which have comparatively large flat surfaces promoting the tendency thereof to adhere through capillary action or surface tension of the treating liquid to the inside surfaces of the flat panels. Such adherence of the workpieces effects a shielding of all or portions of the surface disposed adjacent to the panel surface and moreover restricts the free flow of electric current and free circulation of the treating solution into and out of the treating barrel.

This problem is further aggravated by the progressive pounding-in of the inner surface of the panels of the treating barrel adjacent to the perforations as a result of the impingement of the workpieces thereagainst during the tumbling action. This action causes the formation of burrs and a progressive decrease in the effective diameter of the perforations through the barrel panels significantly restricting the flow of electric current and interfering with the free entry and drainage of the treating solution into and out of the barrel further detracting from the efficiency of the liquid treating operation. The selection of suitable materials to resist this progressive pounding-in of the panel perforations is relatively limited in view of the necessity of employing materials which are resistant to the high temperatures and chemical attack of the acidic and alkaline treating solutions in which the treating barrels are immersed. Synthetic plastic materials such as polymethyl methacrylate, phenol-formaldehyde, and rubber formulations are frequently employed which are resistant to such chemical attack and are of adequate structural strength and which also possess fairly high abrasion resistance to the tumbling action of the workpieces contained therein. Polyethylene and polypropylene are also very desirable because of their comparatively high impact strength but are relatively soft and susceptible to a progressive closing of the perforations as a result of the impingement of the workpieces producing a burr therearound.

It will be appreciated from the foregoing that the combined effect of the abrasion of the interior surfaces and perforations of the barrel panels and the adherence thereto of the relatively small workpieces seriously detracts from the free flow of electric current and free circulation of the treating liquid into and out of the treating barrel with a resultant decrease in the efficiency and uniformity of the treatment of the surfaces of the workpieces. A further factor which presents a problem is that of solution rag-out and drag-in as a result of the impaired drainage characteristics of the treating barrel. Such dragout constitutes a waste of relatively expensive treating solution which coupled with the drag-in of the solution into the adjoining treating receptacles produces contamination of successive treating solutions necessitating a more frequent change thereof to prevent excessive accumulation of the contaminants which impair the efficiency of the treating solution. Alternatively, increased drainage time must be provided to allow the entrapped treating solution to adequately drain from the interior of the treating barrel which substantially increases the length of the processing cycle further detracting from the efliciency and economy of the operation.

It is accordingly a principal object of the present invention to provide an improved treating barrel employing a unique panel construction which substantially overcomes the problems and disadvantages associated with treating barrels of similar type heretofore known.

Another object of the present invention is to provide an improved barrel construction which minimizes adherence of relatively small flat workpieces to the inner surfaces of the barrel thereby maintaining an optimum flow of electric current and circulation of the treating solution into and out of the barrel and preventing unwanted masking of portions of the surfaces of the workpieces.

Still another object of the present invention is to provide an improved treating barrel construction that resists physical abrasion and progressive closure of the perforations through the panels thereof thereby maintaining a continuous high rate of liquid circulation therethrough.

A further object of the present invention is to provide an improved treating barrel construction for treating bulk quantities of relatively small workpieces and which treating barrel facilitates drainage of the treating solutions therefrom substantially reducing solution drag-out and drag-in problems.

Still another object of the present invention is to provide a method for simply providing a texture on the inner surfaces of the improved treating barrel comprising the present invention.

A still further object of the present invention is to provide an improved treating barrel construction which is of high strength and simple design, of durable operation, and of simple and economical operation, maintenance, and manufacture.

The foregoing and other objects and advantages of the present invention are achieved by a treating barrel construction comprising a plurality of longitudinally extending relatively planar side panels and a pair of end panels arranged to define a chamber of polygonal cross section and wherein the side panels are provided with a plurality of perforations therethrough comprising from about to about 35% of the effective area of said panels and wherein the side panels and end panels have the interior faces thereof formed with a plurality of undulations across substantially the entire effective surface thereof extending to a depth of from about 5% to about 50% of the thickness of the panels and disposed at a frequency of about 1 to about 4 undulations per lineal inch.

Other objects and advantages of the present invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings, wherein:

FIGURE 1 is a perspective view of a plating barrel of the general type to which the present invention is applicable rotatably supported at its ends on a typical supporting framework;

FIGURE 2 is an end elevational view of the barrel shown in FIGURE 1 with the supporting framework removed therefrom;

FIGURE 3 is a longitudinal vertical sectional view through the plating barrel shown in FIGURE 2 and taken along the line S3 thereof;

FIGURE 4 is an enlarged fragmentary plan view of the interior face of a side panel of the barrel shown in FIGURE 3 in the encircled area designated 4;

FIGURE 5 is a transverse sectional view through the perforated panel shown in FIGURE 4 and taken along the line 55 thereof.

FIGURE 6 is a fragmentary plan view of an alternate satisfactory configuration of the interior face of a side panel for a plating barrel of the type shown in FIG- URES 1-3;

FIGURE 7 is a fragmentary vertical sectional view through the side panel shown in FIGURE 6 and taken along the line 7-7 thereof;

FIGURE 8 is a fragmentary plan view of another alternate satisfactory surface contour of a side panel for a plating barrel shown in FIGURES l3;

FIGURE 9 is a fragmentary vertical sectional view through the panel shown in FIGURE 8 and taken along the line 9-9 thereof; 1

FIGURE 10 is a fragmentary plan view of still another alternate satisfactory surface contour for the interior face of a barrel side panel;

FIGURE 11 is a fragmentary vertical sectional View of the side panel shown in FIGURE 10 and taken along the line 11-11 thereof;

FIGURE 12 is a fragmentary plan view of yet still another alternate satisfactory surface contour for a barrel side panel;

FIGURE 13 is a fragmentary vertical sectional view of the side panel shown in FIGURE 12 and taken along the line l3-13 thereof, and

FIGURE 14 is a diagrammatic side elevation view of press for embossing a textured pattern on the inner surfaces of the treating barrel panels.

Referring now in detail to the drawings and as may be best seen in FIGURES 13, a typical treating barrel arrangement is shown which is specifically suitable for subjecting bulk quantities of small workpieces contained therein to an electroplating operation. The electroplating apparatus as best shown in FIGURE 1 comprises a plating barrel 2t; of a polygonal cross sectional shape which is rotatably mounted at its end walls 22 on a suitable framework 24. The plating barrel is shown in FIG- URE l with the cover or door panel thereof removed providing visual access to the interior thereof. The

d framework 24 comprises a cross beam as formed with a ring 23 at substantially the midpoint thereof from which the framework and plating barrel thereon can be suspended from a suitable hoist or mechanical conveyor apparatus.

A pair of downwardly extending legs 3% are securely connected at the upper end portions thereof to the cross beam 26. The lower end portions of the legs 38 are formed with rotatable supports on which the end walls 22 of the plating barrel 2%? are rotatably supported. A pair of outwardly extending (rms 32 are connected to the upper end portion of each of the legs 39 and include lugs 34 thereon which are adapted to coact with a suitable current carrying receiving fixture mounted along the upper portion of a treating receptacle or tank (not shown) for appropriately aligning the apparatus as it is lowered into the treating receptacle. The legs 39 also carry suitable conductors 35 which are electrically connected at one of the ends thereof to a pair of electrodes 36 as shown in FIGURE 1, which extend inwardly through substantially the center of the end walls 22 and are adapted to electrically cont; ct and electrify the metallic workpieces contained therein. The other ends of the conductors 3-5 are connected to the lugs 34 which, when disposed in contact with the receiving fixtures on a treating receptacle, can be electrified providing the necessary current for achieving an electroplatiru of the workpieces.

The rotation of the plating barrel 2d while immersed in a treating receptacle may suitably be achieved by the coaction between a driven gear 38 affixed to the exterior of one of the end walls 22 which is disposed in constant meshing relationship with a driving gear 449 rotata ly mounted on the leg 59 of the framework. Rotation of the driving gear 4t may be conveniently achieved by incorporating a suitable motor directly on the framework 2 3 or alternatively, as in the specific arrangement shown in the drawing, an engaging gear may be provided which is adapted to engage with a stationarily mounted motor (not shown), positioned adjacent to and along the upper portions of the treating receptacle and positioned in meshing relationship with the engaging gear 42 when the electroplating apparatus is appropriately aligned and supported on the treating receptacle.

The plating barrel 2% shown in the drawings is of a construction similar to that shown and described in United States Patent No. 2,836,400, granted to William H. Jackson on May 27, 1958, and assigned to the same assignee as the present invention. The plating barrel 20 as shown is of a hexagonal configuration wherein the end walls 22 are of a substantially hexagon shape and are formed with an annular boss 44 fixedly secured at substantially the center of each of the outer surfaces thereof which are adapted to rotatably engage the lower ends of the legs of the framework. It will be understood, however, that the improved plating barrel construction comprising the present invention is equally applicable to plating barrels of this general type having less than or more than six sides. The center of each of the end walls 22 is also provided with a bore 46 through which the electrodes 3-? project into the interior of the plating barrel. A series of radially spaced mounting pads 43 are provided on the exterior face of the right end wall 22 as viewed in FIGURE 3 for securely fastening the driven gear 38 thereto in a manner as shown in FIGURE 1.

The end walls 22 are disposed in longitudinally spaced substantialy parallel relationship and are provided with four longitudinally extending split rails 59 of an irregular polygonal cross sectional shape which extend between and are removably secured at their ends such as by screws 52 to lon 'itudinally aligned corners of the end walls. In the specific construction shown, the rails 56 are of a split construction comprising an inner member 54 and an outer member 56 which are secured together by a series of screws in overlying clamping relationship over the side edges of a series of side panels as. Each of the side panels 66) is substantially planar and of a generally rectangular configuration and define respectively one side of the polygonal shaped plating barrel. The end edges of the side panels 60 as may be best seen in FIGURE 3, are slidably disposed in correspondingly contoured grooves 62 along the inner surfaces of the end walls 22.

The upper portion of the plating barrel 20 as viewed in FIGURES 2 and 3 is formed with a removable door panel 64 which is supported by a pair of closure rails 66 that extend longitudinally between the end walls 22 and are afiixed thereto by suitable screws. The side panels 69 adjacent to the closure rails as are secured tothe inner surfaces thereof by a suitable adhesive or by a series of screws 68 extending inwardly through the closure rail having the shank end portion thereof disposed in threaded engagement in the underlying side panel. The door panel 64 is removably held in a closed position by suitable clamps (not shown) adapted to be positioned in overlying relationship on the exterior surface of the door panel and having the shanks thereof disposed in engagement in a pair of longitudinally extending grooves 70 in the upper portion of the closure rails 66 as best seen in FIGURE 2.

The assembled barrel with the side panels interlocked between the split rails 50 forms an interior surface comprising a plurality of surfaces as defined by the barrel interior faces of the side panels 60 separated at their corners by the inner member 54 of the split rail 50. The inner members 54 are of a generally diamond or rhombic cross sectional shape and serve as longitudinal work deflecting corners or tumbling ribs enhancing the turnover of the workpieces in the barrel during rotation thereof and preventing inadvertent entrapment of the workpieces in the corners. The inner surface of the inner member 54 and the surface of the outer member 56 overlying the side edges of the side panels 60 are formed of an appropriate contour consistent with the particular configuration of the side edges of the side panels to effect a firm interlocking clamping relationship therewith.

The effective interior faces of the side panels exposed to the interior of the plating barrel as Well as the exposed interior face of the door panel 64 are provided with a plurality of perforations 72 therethrough to facilitate circulation of the treating solution into and out of the interior of the plating barrel. The specific size of each of the perforations '72 will vary depending on the particular size and configuration of the small workpieces to be treated therein. Generally, the total area of the perforations will range from about up to about 35% of the effective area of the side panels. A perforated area corresponding to about less than 15% of the effective interior face area of the side panels has been found not to provide adequate fluid circulation into and out of the interior of the barrel whereas a total perforated area of greater than 35% produces an excessive weakening of the panel structure such that fracture or breakage of the panels will occur during the tumbling action of the workpieces therein. It is for this reason that the total perforated area of the effective face of the side panels is limited to between 15% to 35% and preferably to about to about 30%.

As hereinbefore set forth, the impingement of the workpieces Within the plating barrel over prolonged use has heretofore occasioned the formation of burrs and a progressive closure of the perforations adjacent to the interior faces of the side panels particularly when relatively soft materials are used such as polypropylene for example, resulting in a progressive decrease in the porosity of the barrel and a corresponding progressive decrease in the flow of electric current and fluid circulation through the barrel. This factor coupled with the ladhering tendency of relatively small fiat workpieces to the flat interior faces of the side panels and door panel, further detracts from the proper fiuid circulation and particularly the drainage characteristics of the barrel interfering not only with uniform treatment of the surfaces 6 of the workpieces but also causing excessive solution drag-out and drag-in.

In accordance with the improved plating barrel construction comprising the present invention, the interior faces of the side panels, end panels and the door panel are now provided with undulations forming a textured inner surface which serves the dual function of shielding the inner edges of the perforations from direct impingement by the workpieces and also reducing the flat surface area to which the workpieces may adhere substantially completely eliminating their adhering tendency. At the same time, these surface undulations form channels in communication with the perforations which enhance the drainage of the treating solution from the interior of the plating barrel increasing the uniformity of treatment and substantially reducing the solution drag-out and dragin problems heretofore encountered.

One specific embodiment of the improved plating barrel construction comprising the present invention is illustrated in FIGURES 3-5. The undulating or textured interior face of the panel shown in FIGURE 3 is shown in a fragmentary enlarged view in FIGURES 4 and 5. As will be noted in FIGURES 4 and 5, the interior face of the panel is formed with a conically tapered bore 74 disposed in axial alignment with each of the perforations 72 and extending inwardly from the interior face of the panel to a depth of from 5% to 50% of the thickness of the panel. A depth of the conical bores 74 of less than 5% is insufiicient to minimize impingement of the workpieces against the upper edges of the perforations promoting the formation of burrs therearound materially reducing the effective diameter of the perforations. In addition, the shallow depth of the conical bores 74 does not sufficiently reduce the flat surface area of the pane. whereby workpieces have a tendency to adhere to the interior panel surfaces interfering with their proper treatment. On the other hand, conical bores of a depth greater than about 50% produce excessive weakness of the panel and promote engagement of the workpieces therein. It is for this reason that the conical bores are controlled within a range of 5% to 50% of the thickness of the panel and preferably to a depth of from 20% to 25% of the thickness of the panel.

The frequency distribution of the conical bores 74 is dictated by the distribution of the perforations 72 which are controlled within a range of from 1 to 4 per lineal inch in each direction of the panel. The specific frequency within this range employed is established by the diameter of the perforations and the total porosity of ;he hpanel desired within the ranges hereinbefore set ort An alternate satisfactory embodiment of a panel construction is shown in FIGURES 6 and 7 wherein the interior face of the side panel 60 is provided with a plurality of ti-shaped grooves 76 which are defined by the intersection of a surface 78 disposed substantially perpendicular to the plane of the interior face of the panel and a surface 80 angularly inclined relative thereto. The resultant V-shaped grooves 76 form a saw-shaped pattern extending across the inner surface of the panel at a pitch or frequency ranging from one to four per lineal inch. The V-shaped grooves 76can extend longitudinally for substantially the entire length of the panel and preferably are disposed transversely of the length of the panels in substantially parallel spaced relationship. By orienting the grooves in a direction corresponding to the plane of rotation of the barrel, superior drainage characteristics of the solution from the barrel are generally obtained in comparison to a longitudinal or angular disposition of the grooves.

The depth of the grooves 76 are controlled within a range of from 5% to 50% of the panel thickness and preferably from about 20% to 25 of the panel thickness to provide adequate structural strength of the panel and sufficient channeling of the liquid treating solution 7 through the perforations disposed in communication with the grooves 76. The grooves 76 are spaced at the frequency within the aforementioned range without regard to the specific pattern of the perforations 72 through the panel. Conventionally, by this arrangement the major proportion of the periorations are disposed with the inner ends thereof located at least partially within the recessed surfaces of the grooves.

Another alternate satisfactory embodiment of an improved side panel construction is shown in FIGURES 8 and 9 wherein the interior face of the panel 6% is provided with a series of longitudinally extending convex ribs 82 separated by concave grooves 84 forming a serpentine or smooth undulating surface texture. The vertical depth between the crests of the convex ribs and the trough of the adjacent concave groove the is controlled so as to comprise a depth ranging from to 50% of the thickness of the side panel and preferably from 20% to 25 of the thickness. The grooves 84 and ribs 82 extend across substantially the entire effective inner surface area of the panel in spaced substantially parallel relationship and either transversely angularly, or longitudireally of the work-deflecting corners defined by the inner members 54. The grooves 84- and ribs 82 are arranged at a spaced frequency of from one to four per lineal inch to provide adequate liquid channeling and satisfactory strength of the panel and shielding of the inner edges of the perforations 72.

Still another alternative satisfactory embodiment of an improved panel construction comprising the present invention is shown in FIGURES 10 and 11 wherein the interior face of the side panel 6%? is formed with a plurality of discrete depressions 86 of a spherical concave configuration which are disposed in a substantially uniform pattern across substantially the entire inner face of the panel. The depressions 86 are located independently of the perforations 72 whereby the major portion of the perforations are positioned with their upper edges located within the spherical recessed surface of the depressions.

For the same considerations as hereinbefore set forth, the depressions 86 are controlled so as to extend to a depth ranging from 5% to 50% of the panel and preferably from about to about of the thickness thereof. Similarly, the frequency of distribution of the depressions is controlled within a range of 1 to 4 per lineal inch.

Yet still another alternate satisfactory panel construction is shown in FIGURES 12 and 13 wherein the interior face of the side panel 60 is formed with a plurality of longitudinally extending V-shaped grooves 88 of substantially symmetrical cross section which extend across substantially the entire exposed inner surface area of the panel. The V-shaped grooves 88 for the same considerations as hereinbefore set forth, extend to a depth of from 5% to 50% of the thickness of the panel and preferably from about 20% to about 25% of the thickness thereof. The V-shaped grooves similarly are arranged at a frequency of from 1 to 4 per lineal inch thereby providing channels in communication with the perforations '72 facilitating drainage of the treating solution from the interior of the plating barrel.

In each of the panel constructions hereinbefore shown and described, it will be noted that a substantial reduction of the fiat surface area of the inner face of the panel is present which greatly reduces the adhering tendency of small flat workpieces thereto. At the same time, the upper edges of the perforations contiguous to the interior face of the panel are sheltered within a recess, groove, or depression decreasing the likelihood of direct impingement with the workpieces during the tumbling thereof and thereby substantially reducing the formation of a burr therearound obstructing the free flow of treating solution therethrough. It will also be noted that the opening of those perforations which are disposed within a recess, groove, or depression, as provided by the textured inner surface of the panels are of a generally elliptical or other irregular shape which is of a greater area than the cross sectional area of the perforation. This increased area of the opening of the perforations also provides for an increase in the flow of electrical current through the panels of the treating barrel as well as enabling a substantial degree of burring therearound before the effective area thereof is decreased to that of the cross sectional area of the perforation itself within the interior of the panel.

The reduction of the fiat surface area of the panels by virture of the textured surface imparted thereto substantially eliminates the adhering tendency of small flat workpieces thereon whereby in the preferred construction of the treating barrel, the inner surfaces of the end panels 22 are also provided with the textured surface as shown in FIGURES 1 and 2. In FIGURE 1, for example, the inner surface of the end panel 22 is formed with a plurality of concentric concave grooves 84 and convex ribs 82- of the type illustrated in FIGURES 8 and 9 which prevents adherence of the workpieces to the inner surface of end panels during a treating operation. The textured surface or pattern extends over substantially the entire exposed inner surface of the end panels. Any one of the textured patterns such as the V-shaped grooves 76 shown in FIGURES 6 and 7, the convex ribs 82 and concave grooves 84 shown in FIG- URES 8 and 9; the dimpled construction shown in FIG- URES l0 and 11 or the V-shaped grooves 83 as illustrated in FIGURES l2 and 13 can be employed on the interior surface on the end panels at a spacing frequency and depth within the ranges hereinbefore specified. When a grooved pattern is used, the grooves are preferably arranged concentrically relative to the electrode 36 but may also be disposed in straight lines positioned in spaced substantially parallel relationship and extending across the effective interior surface of the end panels. A typical dimpled pattern comprising a plurality of discrete depressions 86 of the type shown in FIGURES l0 and 11 is fragmentarily illustrated in dotted lines on the end panel 22 as shown in FIGURE 2. Conventionally the end panels are not perforated since adequate fiuid circulation and electric current flow is provided through the perforations in the side panels of the treating barrel.

The application of a textured pattern of the desired type as hereinbefore described can be applied to the interior surfaces of the end panels and the side panels by any one of a number of machining techniques and preferably are embossed thereon preliminary to the assembly of the treating bar-rel. In the preferred construction of the treating barrel employing thermoplastic resins such as polyethylene and polypropylene, for example, the desired textured pattern can be hot embossed on the inner surfaces of the panels employing a hot die plate in accordance with the apparatus diagrammatically in FIGURE 14.

As shown in FIGURE 14, a panel such as a side panel 6th of the treating barrel comprised of a thermoplastic resin such as polypropylene, for example, is placed on a platen 91? of a press above which a heated die plate 92 is disposed. The die plate 92 is provided with a plurality of protuberances or propections 94 on the lower face thereof which are located and arranged so as to provide an embossed pattern of the types hereinbefore described. The die plate )2 is supported by suitable rods 96 slidably disposed within tubes 93 and is reciprocable to and from a raised position as shown in FIGURE 14 to a lowered position in which the textured pattern on the lower face of the die plate 92 is disposed in pressure bearing contact against the upper face of the side panel 69. Reciprocation of the die plate to and from the raised position and the lowered position can be achieved by a suitable fluid-actuated cylinder 1% having the end of its rod N2 affixed to substantially the midpoint of the die plate.

The heating of the die plate to the desired temperature can be achieved by any one of a number of means well known in the art such as electrical heating elements 104 embedded at spaced locations around the die plate which are operative to heat the plate and the textured pattern thereon to a temperature sufficient to effect a heat softening of the thermoplastic material of which the panel to be embossed is comprised. For polypropylene, for example, .the die plate is heated to about 325 F. to effect heat softening of the material.

In operation, a panel to be embossed is placed on the platen 90 which itself may be heated if desired, to elevate the temperature of the plastic panel slightly below that at which heat softening thereof will take place. A pre heating of the panel by the heated platen decreases the time required to effect an embossment by the heated die plate when it is lowered into compressive contact against the upper face thereof. The heated die plate 92 is there after lowered by the fluid actuated cylinder 10% whereupon the projections 94 in the lower face thereof are pressed in firm bearing contact against the panel effecting a plastic flow of the thermoplastic resin of which the panel is comprised into the desired textured pattern. After the die plate has become embedded in the panel to the desired depth, the fluid in the fluid-actuated cylinder 1% is reversed and the die plate is retracted after which the panel is removed and allowed to cool. By virtue of this method, no material is lost and the displacement of the plastic while in the heat softened state responsive to the pressure of the die plate forms a smooth textured surface of the desired pattern. The embossment of the panel can be accomplished before the perforations are incorporated in the panel. Conventionally, where the textured panel is independent of the disposition of the perforations through the panel, the embossment is first done followed thereafter by the incorporation of the perforations such as by drilling, for example. In those instances Where the embossed pattern corresponds to the disposition of the perforations such as the conical bores '74 as shown in FIG- URE 4, the em-bossment can be accomplished after the perforations have been incorporated in the panel and in which case the projections on the die plates are disposed at a frequency and are aligned with the centers of the perforations.

It will be apparent from the foregoing that the novel textured pattern of the panels provides for substantially superior treatment of small workpieces in the treating barrel and overcomes the problems heretofore encountered in connection with the treatment of bulk quantities of small parts. By virtue of this construction it is now possible to use relatively soft thermoplastic materials such as polyethylene and polypropylene which are most desirable due to their high impact strength but which heretofore could not be satisfactorily employed due to their low abrasion resistance resulting in the relatively rapid burring of the perforations therethrough.

While it will be apparent that the preferred embodiments herein illustrated are well calculated to fulfill the objects above stated, it will be appreciated that the invention is susceptible to modification, variation and change without departing from the proper scope or fair meaning of the subjoined claims.

What is claimed is:

l. A barrel for liquid treating bulk quantities of small workpieces comprising a pair of longitudinally spaced end walls and a plurality of substantially planar side panels extending between said end walls and positioned with the interior faces thereof defining a chamber of polygonal cross section having longitudinally extending work-deflecting corners, each of said panels formed with a plurality of perforations therethrough positioned substantially uniformly across the surface thereof and comprising from about 15% to about 35% of the total area of said panels, the interior faces of said panels and said end walls formed with a plurality of surface undulations thereon of a depth of from about 5% to about 50% of 10 the thickness of said panels and disposed at a frequency of from about 1 to about 4 undulations per lineal inch.

2. A plating barrel for electroplating bulk quantities of workpieces comprising a pair of longitudinally spaced end walls and a plurality of substantially planar side panels extending between said end walls and positioned with the interior faces thereof defining a chamber of polygonal cross section having longitudinally extending workdeflecting corners, contact means in said barrel for supplying an electrical current to the workpieces therein, each of said side panels formed with a plurality of perforations therethrough positioned substantially uniformly across the surfaces thereof and comprising from about 20% to about 30% of the total area of said panels, the interior faces of said panels and said end walls formed with a plurality of surface undulations thereon of a depth of from about 20% to about 25% of the thickness of said panels and disposed at a frequency of from 1 to 4 undulations per lineal inch.

3. A plating barrel for electroplating bulk quantities of small workpieces comprising a pair of longitudinally spaced end walls and a plurality of substantially planar side panels extending between said end walls and positioned with the interior faces thereof defining a chamber of polygonal cross section having longitudinally extending work-deflecting corners, contact means in said barrel for supplying an electrical current to said workpieces, each of said side panels formed with a plurality of perforations therethrough positioned substantially uniformly across the surfaces thereof and comprising from about 15% to about 35% of the total area of said panels, the interior faces of said panels formed with a conical tapered bore disposed in axial alignment with each of said perforations and extending inwardly to a depth of from 5% to 50% of the thickness of said panels, the interior faces of said end walls formed with a plurality of surface undulations thereon of a depth of from about 5% to about 50% of the thickness of said end walls and disposed at a frequency of from about 1 to about 4 per lineal inch, said perforations and said tapered bores disposed at a frequency of from 1 to 4 per lineal inch.

4. A plating barrel for electroplating bulk quantities of small workpieces comprising a pair of longitudinally spaced end walls and a plurality of substantially planar side panels extending between said end walls and positioned With the interior faces thereof defining a chamber of polygonal cross section having longitudinally extending work-deflecting corners, contact means in said barrel for supplying an electrical current to said workpieces, each of said panels formed with a plurality of perforations therethrough positioned substantially uniformly across the surface thereof and comprising from about 20% to about 30% of the total area of said panels, the interior faces of said panels formed with a conical tapered bore disposed in axial alignment with each of said perforations and extending inwardly to a depth of from 20% to 25% of the thickness of said panels, the interior faces of said end Walls formed with a plurality of surface undulations thereon of a depth of from about 20% to about 25 of the thickness of said end walls and disposed at a fre quency of from about 1 to 4 per lineal inch, said perforations and said tapered bores disposed at a frequency from 1 to 4 per lineal inch.

5. A plating barrel for electroplating bulk quantities of small workpieces comprising a pair of longitudinally spaced end walls and a plurality of substantially planar side panels extending between said end walls and positioned with the interior faces thereof defining a chamber of polygonal cross section having longtiudinally extending work-deflecting corners, contact means in said barrel for supplying an electrical current to said workpieces, each of said panels formed with a plurality of perforations therethrough positioned substantially uniformly across the surface thereof and comprising from about 15 to about 50% of the total area of said panels, the interior faces of said panels and said end walls formed with a plurality of V-shaped grooves defined by one surface disposed substantially perpendicular to the plane of the interior face of said panels and said walls and the other surface angularly inclined thereto and extending across substantially the entire inner surface area of said panels and said walls, said grooves extending inwardly from said interior face to a depth of from to 50% of the thickness of said panels and at a transverse frequency of from 1 to 4 per lineal inch.

6. A plating barrel for electroplating bulk quantities of small workpieces comprising a pair of longitudinally spaced end walls and a plurality of substantially planar side panels extending between said end walls and positioned with the interior faces thereof defining a chamber of polygonal cross section having longitudinally extending work-deflecting corners, contact means in said barrel for supplying an electrical current to said workpieces, each of said panels formed with a plurality of perforations therethrough positioned substantially uniformly across the surface thereof and comprising from about to about of the total area of said panels, the interior faces of said panels and said end walls formed with a plurality of V-shaped grooves defined by the intersection of one surface disposed substantially perpendicular to the plane of the interior faces of said panels and said walls and another surface angularly inclined thereto, said grooves extending across substantially the entire inner surface of said panels and said Walls; said grooves extending inwardly from said interior faces to a depth of from 20% to about 25% of the thickness of said panels and at a transverse frequency of from 1 to 4 per lineal inch.

7. A plating barrel for electroplating bulk quantities of small workpieces comprising a pair of longitudinally spaced end walls and a plurality of substantially planar side panels extending between said end walls and positioned with the interior faces thereof defining a chamber of polygonal cross section having longitudinally extending work-deflecting corners, contact means in said barrel for supplying an electrical current to said workpieces, each of said panels formed with a plurality of perforations therethrough positioned substantially uniformly across the surface thereof and comprising from about 15% to about of the total area of said panels, the interior faces of said panels and said end walls formed with a plurality of convex ribs separated by intervening concave grooves that extend in spaced relationship across substantially the entire inner surface area of said panels and said end walls, the vertical distance from the crest of said ribs to the trough of the adjacent one of said grooves ranging from 5% to of the thickness of said panels, said grooves and said ribs disposed at a frequency of from 1 to 4 per lineal inch.

8. A plating barrel for electroplating bulk quantities of small workpieces comprising a pair of longitudinally spaced end walls and a plurality of substantially planar side panels extending between said end walls and positioned with the interior faces thereof defining a chamber of polygonal cross section having longitudinally extending work-deflecting corners, contact means in said barrel for supplying an electrical current to said workpieces, each of said side panels formed with a plurality of perforations therethrough positioned substantially uniformly across the surface thereof and comprising from about 20% to about 30% of the total area of said panels, the interior faces of said panels and said end walls formed with a plurality of convex ribs separated by intervening concave grooves that extend in spaced relationship across substantially the entire inner surface area of said panels and said walls, the vertical distance from the crest of said ribs to the trough of the adjacent said groove ranging from 20% to 25% of the thickness of said panels, said grooves and said ribs disposed at a frequency of from 1 to 4 per lineal inch.

9. A. plating barrel for electroplating bulk quantities f small workpieces comprising a pair of longitudinally spaced end walls and a plurality of substantially planar side panels extending between said end walls and positioned with the interior faces thereof defining a chamber of polygonal cross section having longitudinally extending worl deflecting corners, contact means in said barrel for supplying an electrical current to said workpieces, each of said panels formed wtih a plurality of perforations therethrough positioned substantially uniformly across the surface therefrom and comprising from about 15% to about 35% of the total area of said panels, the interior faces of said panels and said end walls formed with a plurality of discrete surface undulations disposed substantially uniformly across substantially the entire interior faces of said panels and said walls, said surface undulations extending to a depth of from 5% to 50% of the thickness of said panels and at a transverse frequency of from 1 to 4 per lineal inch.

10. A plating barrel for electroplating bulk quantities of small workpieces comprising a pair of longitudinally spaced end walls and a plurality of substantially planar side panels extending between said end walls and positioned with the interior faces thereof defining a chamber of polygonal cross section having longitudinally extending work-deflecting corners, contact means in said barrel f r supplying an electrical current to said workpieces, each of said panels formed with a plurality of perforations therethrough positioned substantially uniformly across the surface thereof and comprising from about 20% to about 30% of the total area of said panels, the interior faces of said panels and said end walls formed with a plurality of discrete surface undulations of a spherical contour disposed substantially uniformly across substantially the entire interior faces of said panels and said end walls, said surface undulations extending to a depth of from 20% to 25% of the thickness of said panels and disposed at a frequency of from 1 to 4 per lineal inch.

ll. A plating barrel for electroplating bulk quantities of small workpieces comprising a pair of longitudinally spaced end walls and a plurality of substantially planar side panels extending between said end walls and positioned with the interior faces thereof defining a chamber of polygonal cross section having longitudinally extending work-deflecting corners, contact means in said barrel for supplying an electrical current to said workpieces, each of said panels formed with a plurality of perforations therethrough positioned substantially uniformly across the surface thereof and comprising from about 15% to about 35% of the total area of said panels, the interior faces of said panels and said end walls formed with a plurality of V-shaped grooves extending spaced relationship across substantially the entire inner surface of said panels and said end walls, said grooves extending inwardly from said interior faces to a depth of from 5% to 50% of the thickness of said panels and at a transverse frequency of from 1 to 4 per lineal inch.

' 12. A plating barrel for electroplating bulk quantities of small workpieces comprising a pair of longitudinally spaced end walls and a plurality of substantially planar side panels extending between said end walls and positioned with the interior faces thereof defining a chamber of polygonal cross section having longitudinally extending work-deflecting corners, contact means in said barrel for supplying an electrical current to said workpieces, each of said panels formed with a plurality of perforations therethrough positioned substantially uniformly across the surface thereof and comprising from about 20% to about 30% of the total area of said panels, the interior faces of said panels and said end walls formed with a plurality of V-shaped grooves extending across substantially the entire inner surface area of said panels and said end walls in spaced relationship, said grooves extending inwardly from said interior faces to a depth of from 20% to about 13 14 25% of the thickness of said panels and at a transverse 2,932,085 4/60 Allward 29-526 frequency of from 1 to 4 per lineal inch. 2,956,943 10/60 Hoegh 204-213 FOREIGN PATENTS References Cited by the Examiner 813,915 9/51 Germany.

UNITED STATES PATENTS 5 2,216,784 10/40 Payne 29526 JOHN H. MACK, Primary Examiner. 2,243,728 5/41 Davls MURRAY TILLMAN, Examiner 2,836,400 5/58 Jackson 204-213X 

1. A BARREL FOR LIQUID TREATING BULK QUANTITIES OF SMALL WORKPIECES COMPRISING A PAIR OF LONGITUDINALLY SPACED END WALLS AND A PLURALITY OF SUBSTANTIALLY PLANAR SIDE PANELS EXTENDING BETWEEN SAID END WALLS AND POSITIONED WITH THE INTERIOR FACES THEREOF DEFINING A CHAMBER OF POLYGONAL CROSS SECTION HAVING LONGITUDINALLY EXTENDING WORK-DEFLECTIVE CORNERS, EACH OF SAID PANELS FORMED WITH A PLURALITY OF PERFORATIONS THERETHROUGH POSITIONED SUBSTANTIALLY UNIFORMLY ACROSS THE SURFACE THEREOF AND COMPRISING FROM ABOUT 15% TO ABOUT 35% OF THE TOTAL AREA OF SAID PANELS, THE INTERIOR FACES OF SAID PANELS AND SAID END WALLS FORMED WITH A PLURAITY OF SURFACE UNDULATIONS THEREON OF A DEPTH OF FORM ABOUT 5% TO ABOUT 50% OF THE THICKNESS OF SAID PANELS AND DISPOSED AT A FREQUENCY OF FROM ABOUT 1 TO ABOUT 4 UNDULATIONS PER LINEAL INCH. 